Multifunctional Conductive Hydrogel Interface for Bioelectronic Recording and Stimulation

Electrical percolation network based on nano-cellulose template for flexible hydrogel bioelectrode

Hydrogel based electrodes have been applied in the field of bioelectronics, which is of great significance for constructing a robust human-computer interface. However, achieving both reliable conductivity and tissue matching mechanical properties remains challenging. Here, we report a synergistic strategy for constructing a hydrogel electrode for bioelectronic interface with tissue modulus and high conductivity by bacterial cellulose (BC) template induced growth polypyrrole (PPy) electrical percolation network combining a polymethacryloyloxyethyl trimethyl ammonium chloride (PDMC) hydrophilic network. This strategy balances the modulus and conductivity of the bioelectrode, makes up for the adverse effect of the conductive filler on the mechanical properties of the hydrogel, and constructs an effective conductive pathway. The electrical percolation of the hydrogel can be achieved at a low permeability threshold, and the flexibility (E = 288 kPa) of the hydrogel electrode with high conductivity (135.75 S/m) can be obtained. Moreover, the hydrogel electrode has low interface impedance and superior charge storage and injection capability, which allows higher signal-to-noise ratio of recording epidermal electrophysiological signals than that of commercial electrodes. The conductive, flexible and biocompatible hydrogel prepared here provides a new way to construct reliable bioelectronic devices.

Advancing Prosthetic Hand Capabilities Through Biomimicry and Neural Interfaces

Background and ObjectivesProsthetic hand development is undergoing a transformative phase, blending biomimicry and neural interface technologies to redefine functionality and sensory feedback. This article explores the symbiotic relationship between biomimetic design principles and neural interface technology (NIT) in advancing prosthetic hand capabilities.MethodsDrawing inspiration from biological systems, researchers aim to replicate the intricate movements and capabilities of the human hand through innovative prosthetic designs. Central to this endeavor is NIT, facilitating seamless communication between artificial devices and the human nervous system. Recent advances in fabrication methods have propelled brain-computer interfaces, enabling precise control of prosthetic hands by decoding neural activity.ResultsAnatomical complexities of the human hand underscore the importance of understanding biomechanics, neuroanatomy, and control mechanisms for crafting effective prosthetic solutions. Furthermore, achieving the goal of a fully functional cyborg hand necessitates a multidisciplinary approach and biomimetic design to replicate the body's inherent capabilities. By incorporating the expertise of clinicians, tissue engineers, bioengineers, electronic and data scientists, the next generation of the implantable devices is not only anatomically and biomechanically accurate but also offer intuitive control, sensory feedback, and proprioception, thereby pushing the boundaries of current prosthetic technology.ConclusionBy integrating machine learning algorithms, biomechatronic principles, and advanced surgical techniques, prosthetic hands can achieve real-time control while restoring tactile sensation and proprioception. This manuscript contributes novel approaches to prosthetic hand development, with potential implications for enhancing the functionality, durability, and safety of the prosthetic limb.

Electric Stimulation Combined with Biomaterials for Repairing Spinal Cord Injury

Spinal cord injury (SCI) is a central nervous system (CNS) disease with a high disability rate, and reconstructing motor function after SCI remains a global challenge. Recent advancements in rehabilitation and regenerative medicine offer new approaches to SCI repair. Electrical stimulation has been shown to alter cell membrane charge distribution, generating action potentials, and affecting cell behavior. This method aids axon regeneration and neurotrophic factor upregulation, crucial for nerve repair. Biomaterials, used as scaffolds or coatings in cell culture and tissue engineering, enhance cell proliferation, migration, differentiation, and tissue regeneration. Electroactive biomaterials combined with electrical stimulation show promise in regenerating nerve, heart, and bone tissues. In this paper, different types of electrical stimulation and biomaterials applied to SCI are described, and the current application and research progress of electrical stimulation combined with biomaterials in the treatment of SCI are described, as well as the future prospects and challenges.

Bioelectric and physicochemical foundations of bioelectronics in tissue regeneration

Understanding and exploiting bioelectric signaling pathways and physicochemical properties of materials that interface with living tissues is central to advancing tissue regeneration. In particular, the emerging field of bioelectronics leverages these principles to develop personalized, minimally invasive therapeutic strategies tailored to the dynamic demands of individual patients. By integrating sensing and actuation modules into flexible, biocompatible devices, clinicians can continuously monitor and modulate local electrical microenvironments, thereby guiding regenerative processes without extensive surgical interventions. This review provides a critical examination of how fundamental bioelectric cues and physicochemical considerations drive the design and engineering of next-generation bioelectronic platforms. These platforms not only promote the formation and maturation of new tissues across neural, cardiac, musculoskeletal, skin, and gastrointestinal systems but also precisely align therapies with the unique structural, functional, and electrophysiological characteristics of each tissue type. Collectively, these insights and innovations represent a convergence of biology, electronics, and materials science that holds tremendous promise for enhancing the efficacy, specificity, and long-term stability of regenerative treatments, ushering in a new era of advanced tissue engineering and patient-centered regenerative medicine.

Multifunctional Hydrogel Electronics for Synergistic Therapy and Visual Monitoring in Wound Healing

To overcome the limitations of precise monitoring and inefficient wound exudate management in wound healing, an advanced multifunctional hydrogel electronics (MHE) platform based on MXene@MOF/Fe3O4@C photonic crystal hydrogel is developed. This platform combines optical/electrical sensing, synergistic therapy, and real-time visual monitoring into a single, efficient system, offering a comprehensive solution for wound healing. Under photothermal stimulation, the hydrogel releases metal ions that generate hydroxyl radicals, effectively eliminating antibiotic-resistant bacteria. Beyond its antibacterial efficacy, this system offers unprecedented real-time monitoring through temperature-responsive visualization, while structural color changes upon wound exudate absorption provide a clear indication for dressing replacement. By integrating these functionalities, MHE platform allows for precise control of the therapeutic process, significantly improving wound healing and treatment monitoring. The platform's optical/electrical sensing capabilities further broaden its potential applications across other biomedical fields. This breakthrough technology provides clinicians with a powerful tool to optimize therapeutic outcomes, marking a major advancement in wound care and biomedical applications.

Neuromorphic devices for electronic skin applications

Neuromorphic devices represent an important advancement in technology, drawing inspiration from the intricate and efficient mechanisms of the human brain. This review paper elucidates the diverse landscape of neuromorphic electronic skin (e-skin) technologies while highlighting their numerous applications. Here, neuromorphic devices for e-skin are classified as two types of direct neuromorphic e-skins combining both neuromorphic devices and sensors, and indirect e-skins separating neuromorphic devices and sensors. In direct neuromorphic e-skins, there are developing devices like memristor-based neuromorphic devices with sensors and transistor-based neuromorphic devices with sensors. On the other hand, indirect types are demonstrated as separated neuromorphic and sensor parts systems through the various interfacing structures. It also describes recent neuromorphic developments in artificial neural networks (ANNs), deep neural networks (DNNs), and convolutional neural networks (CNNs), for the real-time interpretation of sensory data. Moreover, it introduces multimodal sensory feedback, soft and flexible e-skins, and more intuitive human-machine interfaces. This review examines various applications, including smart textiles for the development of next-generation wearable bioelectronics, brain-sensing interfaces that enhance tactile perception, and the integration of human-machine interfaces aimed at replicating the biological sensorimotor loop, which can improve health monitoring and biomedical applications. Additionally, the review also highlights the potential of neuromorphic e-skin in human-robot interaction, particularly in the context of continuous prosthetic control and robotics. Through this analysis, the paper provides insights into current advancements, identifies key challenges, and suggests future research directions for optimizing neuromorphic e-skin devices and expanding their practical implementation.

Hydrogel-Based Biointerfaces: Recent Advances, Challenges, and Future Directions in Human-Machine Integration

Human-machine interfacing (HMI) has emerged as a critical technology in healthcare, robotics, and wearable electronics, with hydrogels offering unique advantages as multifunctional materials that seamlessly connect biological systems with electronic devices. This review provides a detailed examination of recent advancements in hydrogel design, focusing on their properties and potential applications in HMI. We explore the key characteristics such as biocompatibility, mechanical flexibility, and responsiveness, which are essential for effective and long-term integration with biological tissues. Additionally, we highlight innovations in conductive hydrogels, hybrid and composite materials, and fabrication techniques such as 3D/4D printing, which allow for the customization of hydrogel properties to meet the demands of specific HMI applications. Further, we discuss the diverse classes of polymers that contribute to hydrogel conductivity, including conducting, natural, synthetic, and hybrid polymers, emphasizing their role in enhancing electrical performance and mechanical adaptability. In addition to material design, we examine the regulatory landscape governing hydrogel-based biointerfaces for HMI applications, addressing the key considerations for clinical translation and commercialization. An analysis of the patent landscape provides insights into emerging trends and innovations shaping the future of hydrogel technologies in human-machine interactions. The review also covers a range of applications, including wearable electronics, neural interfaces, soft robotics, and haptic systems, where hydrogels play a transformative role in enhancing human-machine interactions. Thereafter, the review addresses the challenges hydrogels face in HMI applications, including issues related to stability, biocompatibility, and scalability, while offering future perspectives on the continued evolution of hydrogel-based systems for HMI technologies.

MRI and CT compatible asymmetric bilayer hydrogel electrodes for EEG-based brain activity monitoring

The exploration of multi-dimensional brain activity with high temporal and spatial resolution is of great significance in the diagnosis of neurological disease and the study of brain science. Although the integration of electroencephalogram (EEG) with magnetic resonance imaging (MRI) and computed tomography (CT) provides a potential solution to achieve a brain-functional image with high spatiotemporal resolution, the critical issues of interface stability and magnetic compatibility remain challenging. Therefore, in this research, we proposed a conductive hydrogel EEG electrode with an asymmetrical bilayer structure, which shows the potential to overcome the challenges. Benefiting from the bilayer structure with different moduli, the hydrogel electrode exhibits high biological and mechanical compatibility with the heterogeneous brain-electrode interface. As a result, the impedance can be reduced compared with conventional metal electrodes. In addition, the hydrogel-based ionic conductive electrodes, which are free from metal conductors, are compatible with MRI and CT. Therefore, they can obtain high spatiotemporal resolution multi-dimensional brain information in clinical settings. The research outcome provides a new approach for establishing a platform for early diagnosis of brain diseases and the study of brain science.

Hoffmeister Effect Optimized Hydrogel Electrodes with Enhanced Electrical and Mechanical Properties for Nerve Conduction Studies

Flexible epidermal electrodes hold substantial promise in realizing human electrophysiological information collections. Conventional electrodes exhibit certain limitations, including the requirement of skin pretreatment, reliance on external object-assisted fixation, and a propensity of dehydration, which severely hinder their applications in medical diagnosis. To tackle those issues, we developed a hydrogel electrode with both transcutaneous stimulation and neural signal acquisition functions. The electrode consists of a composite conductive layer (CCL) and adhesive conductive hydrogel (ACH). The CCL is designed as a laminated structure with high conductivity and charge storage capacity (CSC). Based on the optimization of Hoffmeister effect, the ACH demonstrates excellent electrical (resistivity of 3.56 Ω·m), mechanical (tensile limit of 1,650%), and adhesion properties (peeling energy of 0.28 J). The utilization of ACH as electrode/skin interface can reduce skin contact impedance and noise interference and enhance the CSC and charge injection capacity of electrodes. As a proof of concept, peripheral nerve conduction studies were performed on human volunteers to evaluate the as-fabricated hydrogel electrodes. Compared with the commercial electrodes, our hydrogel electrodes achieved better signal continuity and lower distortion, higher signal-to-noise ratio (~35 dB), and lower stimulation voltages (up to 27% lower), which can improve the safety and comfort of nerve conduction studies.